Process for production of amphoteric electrolyte resin by continuous bulk polymerization and apparatus for the production

ABSTRACT

A continuous polymerization apparatus is provided for producing an amphoteric electrolyte resin by continuous bulk polymerization at low cost, which apparatus includes a reaction vessel, the reaction vessel including at least four polymerization zones adjacent to each other in series, each polymerization zone being separated by a partition plate, the partition plates admitting a stirring shaft with stirrers, each of the polymerization zones having a thermosensor for sensing temperature within the polymerization zone, a heating device for heating the polymerization zone and a cooling device for cooling the polymerization zone.

This is a divisional application of U.S. application Ser. No. 11/887,186filed Sep. 26, 2007, now U.S. Pat. No. 7,879,957, which is a 371 ofPCT/JP2005/005743 filed Mar. 28, 2005.

TECHNICAL FIELD

The present invention relates to a process for producing a syntheticpolymer component used in industrial fields which paint, ink and thelike pertain to.

More specifically, the present invention relates to a process forproducing a synthetic polymer component used as a binder resin for apigment or the like, an emulsifier for producing the resin, a dispersantfor the pigment or the like, or an additive agent such as a solubilizingagent, a compatibilizer or the like by a continuous bulk polymerizationmethod.

BACKGROUND ART

In the technical field as mentioned above, which the present inventionpertains to, excellent techniques have been developed and put inpractical use by efforts of predecessors, of which the main examples areas follows.

First, Patent Document 1 has provided a continuous bulk polymerizationmethod for obtaining a synthetic polymer component composed of styreneor derivatives thereof, and (meta)acrylic acid, (meta)acrylic acid alkylor the other (meta)acrylic derivative, and having a low molecular weightand a sharp molecular weight distribution, by employing thermalpolymerization. The method has been put in practical use.

Also, Patent Document 2 has provided a continuous bulk polymerizationmethod for obtaining a styrene-(meta)acrylic synthetic polymer componenthaving a low molecular weight and a sharp molecular weight distribution,although it doesn't employ thermal polymerization. The method has beenput in practical use.

Furthermore, Patent Document 3 has provided a continuous bulkpolymerization method for obtaining a (meta)acrylic synthetic polymercomponent having a low molecular weight and a sharp molecular weightdistribution, although it doesn't employ thermal polymerization. Themethod has been put in practical use.

In addition, a continuous bulk polymerization method for a monoalkenylderivative has been also provided (Patent Document 4). The method hasbeen put in practical use.

Furthermore, a continuous bulk polymerization method for a copolymermainly derived from MMA has been also provided (Patent Document 5). Themethod has been put in practical use.

Also, a method for producing a polystyrene having a low molecular weightby employing the combination of a vessel type of polymerization deviceor a pipe type of polymerization device with an extruder has been alsoprovided (Patent Document 6).

Furthermore, a motionless mixer in which a heat carrier can pass in thelast half of a reaction, and a polymerizing method using the same havebeen also provided (Patent Document 7).

However, these continuous bulk polymerization methods do not teach aspecific process for a copolymer as intended by the present inventionwhich contains a radically polymerizable basic monomer and a radicallypolymerizable acidic monomer having a carboxyl group as essentialcomponents, i.e., a continuous bulk polymerization process for anamphoteric electrolyte resin.

The utility of copolymers which contain a radically polymerizable basicmonomer and a radically polymerizable acidic monomer having a carboxylgroup as essential components, i.e., the utility of amphotericelectrolyte resins have been demonstrated in Patent Documents 8 and 9.Also, these Documents describe a process for producing a syntheticpolymer component composed of an amphoteric electrolyte resin by a bulkpolymerization method. However, these documents do not describe aprocess for producing a synthetic polymer components composed of anamphoteric electrolyte resin by a continuous bulk polymerization method.The bulk polymerization method for an amphoteric electrolyte resindescribed in these Documents in fact has a disadvantage that theproduction costs are high.

-   Patent Document 1: JP-B-02-33041-   Patent Document 2: JP-B-05-61284-   Patent Document 3: JP-B-05-58005-   Patent Document 4: U.S. Pat. No. 3,859,268-   Patent Document 5: U.S. Pat. No. 3,968,059-   Patent Document 6: JP-A-2002-37804-   Patent Document 7: JP-A-09-31108-   Patent Document 8: JP-B-1,344,622-   Patent Document 9: JP-B-1,396,151

DISCLOSURE OF THE INVENTION

It is an object of the present invention to establish a continuous bulkpolymerization process for producing an amphoteric electrolyte resin, inwhich the resin can be continuously polymerized and produced at lowcost.

The continuous bulk polymerization method is characterized by the stepsof: continuously feeding a mixture of multicomponent monomers havingcertain different reaction properties to a reaction vessel at a constantrate in a composition designed depending on the reaction properties;reacting the mixture up to a certain reaction yield in the vessel;taking out a reactant at the same rate; separating the remainingunreacted monomers from obtained polymers; totally analyzing thecomposition of the unreacted monomer mixture; compensating the gap withthe designed composition, which correspond to the amount consumed ofeach of the monomers; and thereby continuously supplying a monomermixture with the designed composition to continuously polymerize themixture.

In order to perform a continuous bulk polymerization according to theabove method, required are a device for separating the obtained polymerfrom the residual unreacted monomer mixture; a device for real-timelyand totally analyzing the composition of the residual unreacted monomermixture; and a device for real-timely regulating the composition of asupplied monomer mixture.

Thus, if an apparatus designed according to the requirements is used, acopolymer having a uniform composition distribution together with auniform molecular weight distribution can be manufactured, because amonomer composition to be supplied can be controlled depending on thereaction properties of a polymerization system even when producing acopolymer in the system having extremely different copolymerizingreaction properties.

However, considering the apparatus cost, the method is unsuitable forproducing a wide variety of copolymers in small amounts, although it issuitable for producing copolymers with a predetermined compositiondistribution and molecular weight distribution, in other words, it issuitable for producing a single item mass-producible copolymer.

When producing a wide variety of copolymers having a polar group,neither an emulsion polymerization nor suspension polymerization methodsare employed because of a large restriction on composition. In such acase, a solution polymerization method in a batch style is usuallyemployed. Then, in the method, a manufacturing process as mentionedbelow is generally performed. Firstly, monomers are polymerized bybatch/dropping polymerization processes. In the polymerizationprocesses, the composition of monomers charged into a furnace in advanceand the concentration of an initiator charged into the furnace inadvance, and the composition of the monomers dropped over polymerizationtime and the amount of the initiator dropped over the time have beensuccessfully changed in view of the copolymerizing reaction propertiesof the system. Then, a solvent is removed.

However, this method requires high cost in including the process forremoving the solvent. Also, the batch/dropping polymerization process iscomplicated, although it can result in copolymers having a uniformcomposition distribution and molecular weight distribution. Therefore,for the purpose of avoiding the complexity, a process for polymerizingonly a composition of monomers and an initiator charged in advancewithout additionally dropping them has been performed. The processordinarily requires optimizing the combination and composition ofmonomers charged in order to allow the composition distribution ofobtained copolymers to be within the tolerance level.

In view of the technical matters, the present invention aims atproviding a process for manufacturing various amphoteric electrolyteresins (copolymer) in a small lot with functional monomers havingdifferent polarities, which can result in the amphoteric electrolyteresins having a desired molecular weight and monomer unit compositionratio at low cost; and an apparatus therefor.

A basic technical conception to solve the above problems is as follows.

<1> Taking precise control into much consideration, apparatuses for abatch production with a small size are connected to each other in amulti-stage form to form a small-amount producing apparatus.

<2> The production of a wide variety of resins is developed byinstalling more apparatuses arranged in parallel.

<3> It is made possible to omit a device for separating a residualunreacted monomer mixture and a device for real-timely regulating thecomposition of a supplied monomer mixture by completing a continuousbulk polymerization at a high polymerization reaction yield in aline-sequential reaction apparatus. Also, it is made possible to achievethe molecular weight distribution (Mw/Mn is 1.5 to 10) comparable tothat by usual bulk polymerizations and the polymerization reaction yieldof 0.85 or more, only in one passage.

<4> In order to make the composition distribution of multicomponentcopolymers prepared by continuous bulk polymerization methods as narrowas possible, the copolymerizing reaction properties of monomers to beused are taken into consideration to successfully select a monomercomposition so that copolymers having a uniform composition can beobtained even in a discontinuous bulk polymerization.

Then, in order to solve the above problem, the present inventor paysattention to the following two matters.

(1) The molecular weight depends on the rate of polymerization reaction,and the reaction rate depends on temperature and the concentrations ofmonomers and an initiator to be reacted with. Therefore, how to controltemperature, the concentrations of monomers and an initiator to bereacted with to time axis until they complete passing through reactionzone and the reaction is completed?

(2) The viscosity of fluid to be subjected to polymerization andpressure on it predominantly influence the rate of fluid passing throughreaction zone, and the viscosity of the fluid is defined by themolecular weights and concentration of obtained copolymers andtemperature. Therefore, how to control the temperature of the reactionzone and the feeding way of the fluid associated with the polymerizationin order to constantly hold the rate of the fluid passing through thereaction chamber from a supply port to an outlet port?

The present invention has been made as a result of several attempts onthe above matters.

The present invention relates to a process for producing an amphotericelectrolyte resin by continuous bulk polymerization, which comprises thesteps of:

feeding, from a mixture supply port, a monomer mixture containing 0.01to 10% by weight of at least one radically polymerizable basic monomerhaving a nitrogen atom, 0.01 to 35% by weight of at least one radicallypolymerizable acidic monomer having a carboxyl group and 45 to 99.98% byweight of a monomer capable of copolymerizing with the basic and acidicmonomers, or a mixture of the monomer mixture with a polymerizationinitiator and/or an organic solvent having a boiling point of 80° C. orhigher contained in an amount of 10% by weight or less to the totalweight of the monomers, into a reaction zone composed of fourpolymerization zones which independently provide the mixturetemperatures of the following T₁, T₂, T₃ and T₄:T₁=50 to 160° C., T₂=70 to 190° C., T₃=70 to 250° C., T₄=70 to 270° C.,and T₁<T₂, T₂≦T₃ and T₃≦T₄; and

continuously passing the mixture through the reaction zone with stirringwhile the residence time in each of the polymerization zones iscontrolled to 5 to 20 minutes; whereby

a copolymer is produced in the reaction yield of 85% or higher in onepassage through the reaction zone, and the amphoteric electrolyte resinhas a number average molecular weight of 700 to 6,000 and a Mw/Mn ratioof 1.5 to 10.

Also, in a further aspect, the present invention relates to a continuouspolymerization apparatus capable of being employed for the method asmentioned above. The continuous polymerization apparatus comprises:

a monomer mixture preparation vessel equipped with a heating/coolingdevice and a temperature controlling device for a reflux flow condenser;

a fluid feeding apparatus including a pump for moving a monomer mixturefrom the preparation vessel into a reaction zone and a regulator capableof ON/OFF-controlling the operation of the pump;

a reaction zone including at least four cylindrical polymerization zonesconnected to each other in series via flanges by washer-shaped partitionplates, each of the partition plates having an opening with a diameterof 40 to 80 mm at a center thereof, and each of the polymerization zoneshaving a thermosensor, a jacket for heating and an inner coil forcooling, independently controlling a temperature therein and having aninner diameter of 100 to 150 mmφ and an inner height of 120 to 250 mm;

a stirrer including a stirring shaft penetrating through the centralaxis of the reaction zone and at least one stirring impellers composedof a disk attached to the stirring shaft so as for the shaft to belocated as a center of the disk and a paddle attached thereon, thestirrer being stirred at 50 to 700 rpm, and one or more of the stirringimpeller being attached in an optional direction in the polymerizationzones;

an extraction apparatus attached to the lowest polymerization zone,including a valve and valve automatically opening regulator which have amechanism to enable it to be opened and closed in synchronization withthe fluid feeding rate of the fluid feeding apparatus; and

a fluid level regulator attached to the first polymerization zone,composed of a fluid level sensor and a regulator and regulating a fluidvolume of monomers injected into the reaction zone to constantly hold afluid level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an aspect of a continuouspolymerization apparatus of the present invention. FIG. 1 shows asection in the center of a reaction zone.

FIG. 2 is an enlarged view of a stirring impeller which a continuouspolymerization apparatus of the present invention has.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

In the present invention, examples of radically polymerizable basicmonomers including a nitrogen atom include acrylates such asdimethylaminomethyl acrylate, diethylaminomethyl acrylate,dibutylaminomethyl acrylate, dihexylaminomethyl acrylate,dimethylaminoethyl acrylate, diethylaminoethyl acrylate,di(t-butyl)aminoethyl acrylate, diisohexylaminoethyl acrylate,dihexylaminopropyl acrylate and di(t-butyl)aminohexyl acrylate andmethacrylates corresponding thereto. These may be used independently orin combination.

In the present invention, examples of radically polymerizable acidicmonomers having a carboxyl group include acrylates such as 2-acryloyloxyethyl succinate and 2-acryloyl oxyethyl phthalate as well asα,β-ethylenic unsaturated carboxylic acid such as acrylic acid,methacrylic acid, itaconic acid and maleic acid, and methacrylatescorresponding thereto. These may be used independently or incombination.

In the present invention, examples of monomers capable of copolymerizingwith the monomers as mentioned above include a hydroxyalkyl ester of anacrylic acid or methacrylic acid, for example, monomers such as2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropylacrylate and hydroxypropyl methacrylate. These may be used independentlyor in combination.

Examples of straight-chain or branched-chain (meth)acrylate monomershaving 1 to 18 carbon atoms include monomers such as alkyl ester orcycloalkyl ester of acrylic acid or methacrylic acid, for example,methyl acrylate, methyl methacylate, ethyl acrylate, ethyl methacrylate,n-butyl acrylate, n-butyl methacrylate, i-butyl acrylate, i-butylmethacrylate, t-butyl acrylate, t-butyl methacrylate, cyclohexylacrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, lauryl acrylate and lauryl methacrylate. These may be usedindependently or in combination.

Furthermore, examples of polymerizable monomers which are a styrenederivative include monomers such as styrene and α-methyl styrene. Thesemay be used independently or in combination.

In addition, as other monomers capable of copolymerizing with themonomers as mentioned above, a vinyl monomer such as an acryl amide or amethacryl amide, for example, acryl amide, methacryl amide, N-methylacryl amide, vinyl toluene, vinyl acetate, acrylonitrile andmethacrylonitrile may be used independently or in combination.

Although the monomers as mentioned above may be optionally combined inthe present invention, the combination is preferably selected so that aninstant composition of each copolymer at a polymerization reaction ratekeeps as flat as in the range of the polymerization reaction rate of 0.5to 0.95.

For this end, a Q-e value which predominantly influences a radicalreactivity of each of the monomers and a molar fraction of each of fedmonomers are typically employed. Then, in accordance with a Q-e schemeof Alfrey-Price, a monomer-composition ratio is sequentially calculatedfrom a molar fraction indication of each of monomer units of a copolymerformed from various monomers in an eye blink to semiempirically simulatethe transition of instantaneous copolymer compositions, whereby the fedcomposition may be selected so that the change as mentioned above getsflat. These selections may be executed by employing a personal computerthrough a trial and error process.

However, even if an instant composition of each copolymer at apolymerization reaction rate does not continue to be flat in the rangeof the polymerization reaction rate of 0.5 to 0.95, the combination canbe considered to be adopted to a used object as long as the compositiondistribution does not show a blend system of a copolymer clearly like,for example, an acrylic-vinyl acetate copolymer.

In the present invention, an azo polymerization initiator such asazobisisobutyronitrile and a peroxide polymerization initiator such asbenzoyl peroxide can be used independently or in combination. The amountto be used may be determined so as to obtain copolymers having atargeted molecular weight distribution by some trials on the selectedcombination of the temperatures and the residence times in at least fourpolymerization reaction zones, as mentioned below. However, it ispreferable that the azo initiator is used independently or incombination in order to avoid the formation of branched copolymers.

In the method of the present invention, a chain transfer agent can bealso optionally used. For example, mercaptans such as n-laurylmercaptan, tertiarydodecyl mercaptan and 2-mercaptoethanol, and styrenederivatives such as Nofiner MSD can be used. 2 mercaptoethanol orNofiner MSD having small molecular weight is preferable in good results.

The polymerization initiator may not be necessarily used. A system inwhich a polymerization reaction proceeds without any initiator byraising the temperature may contain no initiator.

The criterion for judgment is as follows:

(a) The radical polymerization reaction tends to proceed in an acidsystem. Therefore, the initiator can be preferably used when using alarge amount of nitrogen-containing monomer which easily makes thesystem to be shifted to an alkali side. When using an initiator, as aresult, the polymerization reaction temperature will be lowered.

(b) When a monomer, solvent or chain transfer agent which are not thepolymerization initiator but has an initiating function exists, noinitiator should be used; the initiator should be used loweringpolymerization temperature; or the amount of an initiator to be usedshould be adjusted depending on polymerization temperatures to be set.Examples of such a compound having an initiating function include anoxyethylene group-containing monomer and a hydroxyl group-containingcompound.

(c) When an acid or basic polar group, particularly, the basic groupexists in small amount, a three-dimensional, reaction such ascross-linking between molecules hardly occurs, or styrene easilythermal-polymerized exists in large amount, the polymerization initiatordoes not have to be used: in other words, so-called thermalpolymerization can be employed.

Thus, it may be determined according to these criterions whether thepolymerization initiator is used. If no initiator is used, it results inhigh temperature polymerization.

The solvents capable of being used in the present invention depend onthe temperature and pressure during reaction in each of thepolymerization zones. The solvents preferably have a large solubility tothe monomer to be used but do not boil at the temperature in thepolymerization zones under pressure. Particularly, an alcohol and aketone, since they have a good solubility to an amino group-containingpolymerization compound, are preferable.

The amount of a solvent to be used is preferably 10% by weight or lessto the total amount of monomers.

However, aromatic compounds such as toluene and xylene; ketones such asacetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols suchas n-butanol, isobutanol and isopropyl alcohol; esters such as ethylacetate and n-butyl acetate; and ether or ester derivatives ofpolyhydric alcohol such as diethylene glycol monoethyl ether or the likecan be employed. These may be used independently or in combination.

Although these solvents may not be essentially used, the use of thesolvents often makes a process stabilized. Therefore, the solvents maybe used if needed.

Next, an apparatus capable of being used for the process of the presentinvention will be described. An example of the apparatuses according tothe present invention is shown in FIG. 1.

In the meantime, a polymerization process according to a bulkpolymerization method is as follows.

In the initial stage of the polymerization, the concentration ofmonomers is high, and the polymerization reaction rate is high. Sincethe concentration of the formed copolymer is still low at this stage,the viscosity of the system is comparatively low.

As the polymerization reaction proceeds, the monomers are consumed, theconcentration of the residual monomers becomes lower, and thepolymerization reaction rate gradually slows down. On the other hand,the concentration of the formed copolymer becomes higher, and thus theviscosity of the system increases.

The molecular weight of the formed copolymer depends on thepolymerization reaction rate. Therefore, it is necessary to hold thepolymerization reaction rate continuously in order to obtain a copolymerhaving a narrow molecular weight distribution. In a polymerizationprocess according to the above bulk polymerization method, for this end,as the polymerization reaction proceeds, it is necessary to raise apolymerization temperature to a suitable one. As a result, thepolymerization temperature is controlled over time so as to obtain aconstant polymerization reaction rate.

In view of this point, the present invention performs a polymerizationreaction by continuously moving a mixture subjected to polymerization ata certain temperature into a different environment at a highertemperature. It should be obvious that it is preferable to increase thenumber of the transitions to other temperature environments as much aspossible in order to perform this process ideally. However, the presentinventors have found out that a substantially constant polymerizationreaction rate is obtained by the transitions of at least four times.Thus, this discovery results in a continuous bulk polymerization methodby four polymerization zones.

Also, although the viscosity of the system is increased as thepolymerization reaction proceeds, the level of the viscosity is varieddepending on the molecular weights (distribution) of the copolymers inthe system. Even if the environment at high temperature is provided, itis most difficult to hold a constant viscosity until the completion ofthe polymerization.

Therefore, typically, the movement to the four polymerization zoneswhich have different temperature environments would be performed byemploying separate fluid feeding pumps and separate vessels withpolymerization zones of different sizes designed in view of each of theresidence times. However, the apparatus of the present invention may nothave such structures.

The apparatus of the present invention comprises:

a monomer mixture preparation vessel equipped with a heating/coolingdevice and a temperature controlling device for a reflux flow condenser;

a fluid feeding device including a metering pump for feeding a monomermixture from the preparation vessel into a reaction zone and a regulatorcapable of ON/OFF-controlling the operation of the pump;

a reaction zone including at least four cylindrical polimerization zonescontinuously and vertically connected with each other via flanges bywasher-shaped partition plates, each of the partition plates having anopening with a diameter of 40 to 80 mm at a center thereof, each of thepolymerization zones having an inner diameter of 100 to 150 mmφ and aninner height of 120 to 250 mm, having a thermosensor, a jacket forheating and an inner coil for cooling, and capable of independentlycontrolling temperatures therein, the mixture temperatures of T₁° C.,T₂° C., T₃° C. and T₄° C. in the first, second, third and fourthpolymerization zones from the top being capable of being respectivelycontrolled so as to satisfy the following expressions: T₁=50 to 160° C.,T₂=70 to 190° C., T₃=70 to 250° C., T₄=70 to 270° C., and T₁<T₂, T₂≦T₃and T₃≦T₄;

a stirrer including at least one or more stirring impeller (see FIG. 2)composed of a disk of 40 to 100 mmφ and a paddle impeller attached ontothe disk and consisting of two parts which constitute a diameter of thedisk, the stirring impeller being attached in an optional direction ineach of the zones to a stirring shaft penetrating through the reactionzone, and the stirrer being capable being stirred at 50 to 700 rpm;

an extraction device attached to the lowest polymerization zone, andincluding a valve and automatically valve opening regulator which have amechanism to enable the valve to open and close in synchronization witha fluid feeding rate of the fluid feeding device; and

a fluid level regulator attached to the first polymerization zone, andcomposed of a fluid level sensor and a regulator, the fluid level sensorregulating a fluid volume of monomers fed into the reaction zone toconstantly hold a fluid level.

The continuous polymerization apparatus can feed a reactant underpressure of 0.05 MPa to 5 MPa from a supply pump at the upper part,regulate residence time of a mixture (including polymerization productsas the reaction proceeds) in each of the zones within 5 to 20 minutes,and take out the reactant from the fourth zone, whereby a continuousbulk polymerization method for an amphoteric electrolyte resin accordingto the present invention is performed to produce a copolymer in areaction yield of 85% or more through one fluid passage.

First, referring to a reaction vessel, it has been built up byconnecting cylindrical polymerization zones with the same size within aminimized diameter of 100 to 150 mmφ and a length of 120 to 250 mm witheach other by simple partition plates. As a result, a middle pumps areomitted, and all the fluid movement is performed by the supply pump atthe first polymerization zone.

Referring to a temperature condition, if the first, second, third andfourth polymerization zones from the top provide the mixturetemperatures of T₁° C., T₂° C., T₃° C. and T₄° C., respectively, T₁, T₂,T₃ and T₄ are respectively controlled so as to satisfy the followingexpressions: T₁=50 to 160° C., T₂=70 to 190° C., T₃=70 to 250° C., T₄=70to 270° C., and T₁<T₂, T₂≦T₃ and T₃≦T₄. More preferably, in theexistence of an initiator, the mixture temperatures of T₁, T₂, T₃ and T₄in four polymerization zones satisfy the following expressions: T₁=50 to100° C., T₂=70 to 120° C., T₃=70 to 150° C., T₄=70 to 180° C., T₁<T₂,T₂≦T₃ and T₃≦T₄.

Also, in the absence of any initiator, preferably, the mixturetemperatures of T₁, T₂, T₃ and T₄ in four polymerization zones satisfythe following expressions: T₁=100 to 160° C., T₂=100 to 200° C., T₃=100to 240° C., T₄=100 to 270° C., T₁<T₂, T₂≦T₃ and T₃≦T₄.

If the polymerization scale is enlarged, it is preferable to provide theapparatuses in parallel.

In the apparatus of the present invention, in order to smoothly movefluid having different viscosities in the reaction zone, the cylindersof the polymerization zones may be vertically connected with each other,a stirring shaft penetrating through the reaction zone be provided, andstirring impellers be attached to the shaft in a different form in eachof the polymerization zones.

A diameter D2 of a stirring impeller may be designed to be set to a rateof 0.3 to 0.8 to a cylindrical inner diameter D1 of a reaction zone,preferably a rate of 0.35 to 0.6. According to one preferable example,the arrangement of a stirring impeller is as follows (see FIG. 1).

The first polymerization zone: one stirring impeller in which a paddleimpeller is attached onto the upper surface of a disk.

The second polymerization zone: the same stirring impellers are set atthe upper and lower positions.

The third polymerization zone: the same as above.

The fourth polymerization zone: a stirring impeller is set at the upperposition, and another is set at the lower position with paddle side facedownward.

The rotational speed of the shaft may be 50 to 700 rpm. The rotationalspeed is preferably 200 to 400 rpm, but it may be suitably selecteddepending on the viscosity of the system.

The fluid feeding rate may be generally 0.2 to 2 kg/min, and preferably0.3 to 0.82 kg/min.

This may be optionally selected depending on the properties of thesystem.

The pressure of the pump may be adjusted to satisfy this condition. Thepressure is preferably 0.05 MPa to 0.5 MPa.

EXAMPLES

Hereinafter, the present invention will be described in further detailswith working examples.

Example 1 Preparation of Monomer Mixture

Materials to be used were previously stirred and mixed in a vessel madeof SUS. The composition is as follows.

TABLE 1 stylene 43.17% by weight butyl acrylate 18.58% by weight acrylicacid 26.54% by weight diethylaminoethyl metacrylate  4.42% by weight2-mercaptoethanol  6.63% by weight2,2′-azobis(2,4-dimethylvaleronitrile)  0.40% by weight1,1′-azobis(cyclohexane-l-carbonitrile)  0.09% by weight

Preparation of Reactor

A single pipe made of stainless steel which have the size of 130 mmφ×150mm H and a thickness of 5 mm and flanges at both ends, a jacket havingan electric heater for heating outside of the single pipe, and athermosensor and an inner coil for cooling-inside of the single pipe areemployed to constitute a polymerization zone. When each of the flangeswas connected, a disk made of stainless steel and having an opening with65 mmφ at the center and a thickness of 2 mm was used as a partitionplate, and four polymerization zones were vertically connected with eachother to form a reaction vessel having the first, second, third andfourth polymerization zones from the top.

A material inlet port, a stirring shaft, a stirrer and a pressure gaugewere provided at the top flange of the first polymerization zone. Anoutlet port for taking out the reactant was formed at a bottom flange ofthe fourth polymerization zone, and each of the polymerization zonescould be automatically and independently controlled over the innertemperature.

For stirring in each of the polymerization zones, the following isprovided: a stainless steel shaft with 12 mmφ penetrating through eachof the polymerization zones, and seven stirring impellers in which twopaddle impellers having a height of 14 mm were attached onto a disk of50 mmφ having a thickness of 2 mm without sticking out of the perimeterof the disk. These stirring impellers were respectively located in eachof the polymerization zones as follows:

-   -   The first polymerization zone: A stirring impeller was located        at the middle position and its paddle impeller has upward face.    -   The second polymerization zone: Two stirring impellers were        located so that the zone was divided into three and their paddle        impellers have upward faces.    -   The third polymerization zone: The same as the above.    -   The fourth polymerization zone: Two stirring impellers were        located so that the zone was divided into three. The paddle        impeller at the upper position has upward face, but the paddle        impeller at the lower position has downward face.

Thus, the contents is hardly mixed between the polymerization zones dueto the existence of plate parts, and the contents is sufficiently mixedup in the polymerization zones due to the existence of the paddle partsto result in a desirable state where the flow from the top to the bottomis close to laminar flow rather than turbulent flow.

Polymerization Procedure:

First, while closing the outlet port, a monomer mixture as method abovewas charged in the fourth polymerization zone at room temperature andthe temperature was raised so as to be set to 80° C. in 10 minutes.

After 10 minutes, another monomer mixture was charged into the thirdpolymerization zone at room temperature and the temperature was raisedso as to be set to 80° C. in 10 minutes. Meanwhile, the temperature inthe fourth polymerization zone was adjusted so as to be held at 80° C.

After 20 minutes in total, another monomer mixture was charged into thesecond polymerization zone at room temperature, and the temperature wasraised so as to be set to 80° C. in 10 minutes. Meanwhile, thetemperature in the third polymerization zone was held at 80° C.Simultaneously, the temperature in the fourth polymerization zone wasraised to 100° C. in 2 to 3 minutes, and was held at 100° C.

After 30 minutes in total, another monomer mixture was charged into thefirst polymerization zone at room temperature, and the temperature wasraised so as to be set to 80° C. in 10 minutes. Meanwhile, thetemperature of the second polymerization zone was held at 80° C.Simultaneously, the temperature of the third polymerization zone wasraised to 100° C. in 2 to 3 minutes, and was held at 100° C. The fourthpolymerization zone was promptly raised from 100° C. to 120° C., and washeld at 120° C.

According to the procedure as mentioned above, after 30 to 40 minutes intotal, the following temperature pattern could be formed in thepolymerization zones:

-   -   The first polymerization zone: raising of from room temperature        to 80° C.;    -   The second polymerization zone: holding of the temperature at        80° C.;    -   The third polymerization zone: raising of from 80° C. to 100° C.        and holding the temperature at 100° C.; and    -   The fourth polymerization zone: raising of from 100° C. to        120° C. and holding the temperature at 120° C.

After 40 minutes in total, the outlet port was opened. Then, a newmonomer mixture was charged into the first polymerization zone at roomtemperature while continuously taking out the reactant from the fourthpolymerization zone. The amount to be charged was adjusted so that totalresidence time during the whole process was set to 40 minutes, and thetemperature was controlled so that the temperature conditions in thepolymerization zones showed the pattern as mentioned above. The reactantwas then taken out at a constant speed.

The above process was continued, it was confirmed that the processreached to the stationary state, and then the reactant was taken out tobe characterised.

The resin obtained thus had the following characteristics:

TABLE 2 polymerization reaction yield 94.1% number average molecularweight Mn: 1,589 weight average molecular weight Mw: 14,623 dispersiondegree Mw/Mn: 9.2

This resin was completely dissolved at concentration of 50% in a mixedsolvent of 7/3 of xylene/isopropyl alcohol, and completely andtransparently dissolved at a concentration of 30% in aqueous ammoniawater.

Example 2

A monomer mixture having the following composition was prepared.

TABLE 3 Compounds % by weight styrene 42.41 butyl acrylate 18.17 acrylicacid 12.98 methacrylic acid 12.98 diethylaminoethyl methacrylate 4.332-mercaptoethanol 4.33 isopropyl alcohol 4.332,2′-azobis(2,4-dimethylvaleronitrile) 0.391,1′-azobis(cyclohexane-1-carbonitrile) 0.09

The same apparatus and operation as those used in Example 1 were used topolymerize the mixture.

The obtained resin had the following characteristics:

-   -   polymerization reaction yield: 89.3%    -   number average molecular weight Mn: 1,940    -   weight average molecular weight Mw: 16,783    -   dispersion degree Mw/Mn: 8.6

This resin was transparently dissolved at a concentration of 50% in amixed solvent of xylene/ethyl acetate/isopropyl alcohol: 4/4/2, andcompletely and transparently dissolved at a concentration of 30% inaqueous ammonia.

Example 3

A monomer mixture having the following composition was prepared.

TABLE 4 Compounds % by weight styrene 27.88 butyl acrylate 27.88 acrylicacid 23.89 diethylaminoethyl methacrylate 3.98 2-mercaptoethanol 7.96isopropyl alcohol 7.96 2,2′-azobis(2,4-dimethylvaleronitrile) 0.361,1′-azobis(cyclohexane-1-carbonitrile) 0.08

The same apparatus and operation as those used in Example 1 were used topolymerize the mixture.

The obtained resin had the following characteristics:

TABLE 5 polymerization reaction yield: 97.1% number average molecularweight Mn: 1,068 weight average molecular weight Mw: 4,505 dispersiondegree Mw/Mn: 4.2

The resin was dissolved at a concentration of 50% in a mixed solvent ofxylene/isopropyl alcohol: 7/3, and completely dissolved at aconcentration of 30% in a monoethanolamine aqueous solution.

Example 4

A monomer mixture having the following composition was prepared:

TABLE 6 Compounds % by weight styrene 27.90 ethyl acrylate 27.90 acrylicacid 23.91 diethylaminoethyl methacrylate 3.99 2-mercaptoethanol 7.97isopropyl alcohol 7.97 2,2′-azobis(2,4-dimethylvaleronitrile) 0.36

The same apparatus as that used in Example 1 was used. The mixture waspolymerized in the same manner as that in Example 1 except that theresidence time of each of the polymerization zones was changed from 10minutes to 15 minutes and the mixture temperature of each of thepolymerization zones other than the first polymerization zone was set to80° C. Therefore, all the reaction time becomes 60 minutes.

The resin obtained thus had the following characteristics:

-   -   polymerization reaction rate: 96.2%    -   number average molecular weight Mn: 1,091    -   weight average molecular weight Mw: 3,983    -   dispersion degree MW/Mn: 3.7

This was dissolved at a concentration of 50% in a mixed solvent oftoluene/ethyl acetate/ethanol: 4/4/2 and transparently dissolved at aconcentration of 30% in aqueous ammonia.

Example 5

A monomer mixture having the following composition was prepared:

TABLE 7 Compounds % by weight methyl methacrylate 27.93 butyl acrylate27.93 acrylic acid 23.94 diethylaminoethyl methacrylate 3.992-mercaptoethanol 7.98 isopropyl alcohol 7.982,2′-azobis(2,4-dimethylvaleronitrile) 0.29

The same apparatus as that of Example 1 and the same operation as thatof Example 4 were used to polymerize the mixture.

The resin obtained thus had the following characteristics:

TABLE 8 polymerization reaction yield: 97.5% number average molecularweight Mn: 1,303 weight average molecular weight Mw: 2,135 dispersiondegree Mw/Mn: 1.6

The resin was dissolved at a concentration of 50% in a mixed solvent ofxylene/isopropyl alcohol: 8/2, and completely dissolved at aconcentration of 30% in a morpholine aqueous solution.

Example 6

A monomer mixture having the following composition was prepared:

TABLE 9 Compounds % by weight Styrene 13.97 methyl methacrylate 13.97butyl acrylate 27.93 acrylic acid 23.94 diethylaminoethyl methacrylate3.99 2-mercaptoethanol 7.98 isopropyl alcohol 7.982,2′-azobis(2,4-dimethylvaleronitrile) 0.24

The apparatus of Example 1 and the operation of Example 4 were used topolymerize the above monomers. As a result, a resin having the followingcharacteristics was obtained:

-   -   polymerization reaction yield: 98.5%    -   number average molecular weight Mn: 1,187    -   weight average molecular weight Mw: 3,619    -   dispersion degree Mw/Mn: 3.0

This was dissolved at a concentration of 50% in a mixed solvent ofxylene/ethanol:8/2, and transparently dissolved at a concentration of30% in ammonia water.

Example 7

A monomer mixture having the following composition was prepared, and washeld at room temperature.

TABLE 10 Compounds % by weight 2-hydroxyethyl methacrylate 9.202-ethylhexyl methacrylate 5.03 diethylaminoethyl methacrylate 44.43methacrylic acid 6.07 Styrene 4.16 methyl methacrylate 17.702-mercaptoethanol 4.34 isopropyl alcohol 8.682,2′-azobis(2,4-dimethylvaleronitrile) 0.39

The same apparatus as that of Example 1 was used. The mixture waspolymerized in the same manner as in Example 4 except that the residencetime of each of the zones was changed from 10 minutes to 11 minutes andthe temperature of each of the polymerization zones other than the firstpolymerization zone was set to 80° C. Therefore, all the reaction timebecomes 46 minutes.

The resin obtained thus had the following characteristics:

Table 11 polymerization reaction rate: 95.4% number average molecularweight Mn: 1,756 weight average molecular weight Mw: 3,007 dispersiondegree Mw/Mn: 1.7

This resin was completely dissolved at a concentration of 50% in a mixedsolvent of xylene/ethanol:7/3, and dissolved at a concentration of 30%in aqueous ammonia.

Example 8

A monomer mixture having the following composition was prepared, and washeld at room temperature.

TABLE 12 Compounds % by weight 2-hydroxyethyl methacrylate 19.922-ethylhexyl methacrylate 10.91 diethylaminoethyl methacrylate 27.53methacrylic acid 4.68 styrene 4.50 methyl methacrylate 19.052-mercaptoethanol 4.34 isopropyl alcohol 8.682,2′-azobis(2,4-dimethylvaleronitrile) 0.39

The same apparatus as that of Example 1 and the same operation as thatof Example 7 were used to polymerize the above monomer mixture.

TABLE 13 polymerization reaction rate: 93.7% number average molecularweight Mn: 2,146 weight average molecular weight Mw: 3,797 dispersiondegree Mw/Mn: 1.8

As a result, the resin was completely dissolved at a concentration of50% in a mixed solvent of xylene/ethanol:7/3, and dissolved at aconcentration of 30% in aqueous ammonia.

Example 9

A monomer mixture having the following composition was prepared, and washeld at 80 to 100° C.

TABLE 14 Compounds % by weight styrene 44.15 butyl acrylate 18.92acrylic acid 27.02 dimethylaminoethyl methacrylate 0.10 Nofmer MSD 9.81

The same apparatus as that of Example 1 and the same operation as thatof Example 1 were used to polymerize the above monomer mixture exceptthat the temperatures of the first zone, second zone, third zone andfourth zone were respectively 150° C., 180° C., 230° C. and 250° C.; andthe residence time of each of the zones was set to 8 minutes.

The obtained resin had the following characteristics:

-   -   polymerization reaction yield: 96.6%    -   number average molecular weight Mn: 1,431    -   weight average molecular weight Mw: 6,113    -   dispersion degree Mw/Mn: 4.3

The resin was completely dissolved in a mixed solvent ofxylene/ethanol:7/3, and transparently dissolved at a concentration of30% in aqueous ammonia.

Example 10

A monomer mixture having the following composition was prepared, and washeld at 80 to 100° C.

TABLE 15 Compounds % by weight styrene 17.32 methyl methacrylate 17.32butyl acrylate 34.64 acrylic acid 27.66 dimethylaminoethylmethacrylate0.10 2-mercaptoethanol 2.97

The same apparatus as that of Example 1 was used, and the temperatureand operation of each of the zones were used and performed according toExample 9; to polymerize the above monomer mixture.

The obtained resin had the following characteristics:

TABLE 16 polymerization reaction yield: 96.4% number average molecularweight Mn: 1,591 weight average molecular weight Mw: 5,025 dispersiondegree Mw/Mn: 3.2

This resin was completely dissolved in a mixed solvent ofxylene/ethanol:7/3, and transparently dissolved at a concentration of30% in aqueous ammonia.

Comparative Example 1

The same monomer composition as that of Example 1, and an apparatushaving the conventional paddle type impeller instead of all the stirringimpellers of the apparatus used in Example 1 was used to polymerize themonomer composition according to Example 1. The monomer moved at a blastthrough the shaft to a lower exit. The polymerization did not proceed.

Comparative Example 2

Instead of all the stirring impellers in used Comparative Example 1,conventional plate type impellers were used to perform thepolymerization. However, the reaction temperature was raised like arunaway reaction, and the reaction temperature could not be controlledto fail the polymerization.

INDUSTRIAL APPLICABILITY

Functional substances such as pigments used in industrial fields whichpaint, ink and the like pertain to cannot exhibit the functionindependently. They essentially exhibit the function only after they aredispersed in the binder resin as a medium.

Therefore, functional substances such as pigments having various acidicand basic chemical characteristics on the surface inevitably requiredvarious chemical properties for binder resins for the substances, i.e.synthetic polymer components.

For the requirements, synthetic polymer components used in the fieldsordinarily contain a binder resin as main components as well as adispersant in conformity with the acidic and basic chemical propertieson the surface of each of the functional substances, an emulsifier forthe resin, or an additive agent such as a solubilizing agent orcompatibilizer for mediating the resin and the dispersant. Thus, thesynthetic polymer components used in the fields are essentially productswith diverse functions, and they are produced in small lots.

It has been understood that so-called amphoteric electrolyte resinshaving both acidic and basic functions are useful as the above syntheticpolymer components. However, there has been no means for producingamphoteric electrolyte resins having low molecular weights and a narrowmolecular weight distributions at low cost.

The present invention overcomes this problem, and thus has a largecontribution in the fields.

1. A continuous polymerization apparatus comprising: a reaction vesselbeing substantially cylindrical, having a first end plate flange with amonomer mixture inlet port there through and a second end plate flangeat the distal end of the reaction vessel, with a polymer outlet portthere through, said first end plate further having a hole, substantiallycircular, located at a center axis of the cylindrical reaction vessel topass through a stirring shaft along the axis of the reaction vessel,wherein the reaction vessel includes, at least four polymerization zonesadjacent to each other in series, there being a first and a lastpolymerization zone, along the axis of and inside the reaction vessel,each polymerization zone being separated by a partition plate, eachpartition plate having an opening located at the center axis of thereaction vessel thereof to pass through the stirring shaft, each of thepolymerization zones having a thermosensor for sensing temperaturewithin the polymerization zone, a heating device for heating thepolymerization zone and a cooling device for cooling the polymerizationzone, and a stirrer including a rotatable stirring shaft along the axisof the reaction vessel extending to be in each polymerization zone, andat least one stirring impeller attached to the stirring shaft which islocated within each polymerization zone.
 2. The continuouspolymerization apparatus of claim 1, wherein: the heating deviceincludes a heating jacket circumferentially surrounding the outside ofthe reaction vessel corresponding to the polymerization zone within; andthe cooling device includes a cooling coil inside the reaction vessel.3. The continuous polymerization apparatus of claim 1, wherein thethermosensor, and at least one of the heating device and cooling devicein each of the polymerization zones, independently control a mixturetemperature in each of the polymerization zones so that the mixturetemperature in a polymerization zone is higher than the temperature in apreceding polymerization zone through which the mixture passed.
 4. Thecontinuous polymerization apparatus of claim 3, wherein the reactionvessel includes four polymerization zones, and the mixture temperaturestherein, T₁, T₂, T₃ and T₄, satisfy the following expressions:T₁=50 to 160° C., T₂=70 to 190° C., T₃=70 to 250° C., T₄=70 to 270° C.,and T₁<T₂, T₂<T₃ and T₃<T₄.
 5. The continuous polymerization apparatusof claim 1, wherein said stirring impeller includes, an disk shapedplate, having a center and two flat surfaces, which is attached to thestirring shaft wherein the shaft is located at the center of the disk,and a paddle affixed to and protruding from a surface of the disk. 6.The continuous polymerization apparatus of claim 1, wherein a ratio,D2/D1, of a diameter D2 of the stirring impeller to a cylindrical innerdiameter D1 of the reaction vessel is 0.3 to 0.8.
 7. The continuouspolymerization apparatus of claim 5, wherein the stirring impeller ispositioned in any direction in each of the polymerization zones.
 8. Thecontinuous polymerization apparatus of claim 7, wherein the reactionvessel is vertically oriented, includes four polymerization zones, andthe stirring impellers are positioned within the zones as follows: 1)within the first polymerization zone, one stirring impeller has onepaddle protruding from the upper surface of the impeller disk; 2) withinthe second polymerization zone, there are two stirring impellers whereineach stirring impeller has one paddle protruding from the upper surfaceof the impeller disk; 3) within the third polymerization zone, there aretwo stirring impellers wherein each stirring impeller has one paddleprotruding from the upper surface of the impeller disk; and 4) withinthe fourth polymerization zone, there are two stirring impellers whereinone stirring impeller has one paddle protruding from the upper surfaceof the impeller disk and the second impeller has one paddle protrudingfrom the lower surface of the impeller disk.
 9. The continuouspolymerization apparatus of claim 1, wherein each of the partitionplates has an opening with a diameter of 40 to 80 mm at a centerthereof, and each of the polymerization zones has an inner diameter of100 to 150 mm and an inner height along the axis of 120 to 250 mm. 10.The continuous polymerization apparatus of claim 1, further comprising afluid feeding apparatus including a pump for moving a monomer mixture ata fluid feed rate.
 11. The continuous polymerization apparatus of claim10, wherein said pump consists of a pump for moving the monomer mixturefrom the monomer mixture preparation vessel into the firstpolymerization zone.
 12. The continuous polymerization apparatus ofclaim 11, wherein the reaction vessel is oriented vertically.
 13. Thecontinuous polymerization apparatus of claim 11, wherein the pumpapplies pressure so that residence time of a mixture in each of thezones is regulated within 5 to 20 minutes.
 14. The continuouspolymerization apparatus of claim 1, wherein each portion of thereaction vessel containing a polymerization zone is connected with eachother in series via flanges.
 15. The continuous polymerization apparatusof claim 1, further including a monomer mixture preparation vesselequipped with a heating/cooling device and a temperature controllingdevice.
 16. The continuous polymerization apparatus of claim 1, whereinthe opening at the center of each partition plate is substantiallyround.
 17. The continuous polymerization apparatus of claim 10, furtherincluding an extraction apparatus, having an extraction valve and anextraction valve regulator for moving a polymer product from the lastreaction zone through the polymer outlet port of the reaction vessel.18. The continuous polymerization apparatus of claim 17, furtherincluding a control mechanism to operate the extraction valve regulatorto open and close in synchronization with the fluid feed rate of thefluid feeding apparatus.
 19. The continuous polymerization apparatus ofclaim 10, further including a fluid level regulator, having a fluidlevel sensor located within the first polymerization zone, the fluidlevel regulator controlling the fluid feed rate of the fluid feedingapparatus.